Present refrigeration cycles reject heat to the atmosphere. In some cases a portion of the energy which would otherwise be rejected may be recovered from the cycle, thereby increasing the overall efficiency.
FIG. 1 shows a diagrammatic representation of a heat pump circuit of the prior art. Hot, high pressure refrigerant liquid enters a throttling device, often referred to as a Tx valve, which reduces its pressure and temperature at constant enthalpy. The heat absorbing vapour is passed through a heat exchanger or “evaporator ” which absorbs heat from ambient temperature air blown across its surfaces by a fan, cooling the air and thereby providing the refrigeration effect and causing it to expand. The acquisition of heat causes the liquid to flash to vapour and expand.
The heat laden working fluid vapour is then passed into an accumulator which has an internal structure designed to allow any remaining liquid to boil off prior to entering the compressor.
The energy rich warm working fluid vapour enters a compressor, which as a result of a work input, compresses the vapour thus raising its temperature and pressure. A significant portion of the work input into the compressor re-appears as the heat of compression thus superheating the working fluid vapour.
The superheated working fluid vapour thus has its temperature elevated above that of the ambient temperature of the environment and enters a condenser, which has a structure similar to that of the evaporator. A heat exchange then occurs between the superheated working fluid vapour and the environment which is at a lower temperature. The heat exchange continues until sufficient heat is removed from the working fluid to cause a change of state from hot vapour to hot liquid.
The hot working fluid liquid enters a reservoir, usually referred to as a “receiver” which has a sufficiently large volume to support the requirements of the thermodynamic cycle and withstand the high pressure in the discharge line of the compressor. The hot high pressure refrigerant liquid then enters the TX valve to complete the thermodynamic cycle.
Air conditioning systems have become a huge draw on electricity power in many of the major cities of the world and are viewed as an essential component of many large buildings in order to maintain a level of environmental control within the building. At the same time as air conditioning systems continue to increase in number, it is becoming increasingly recognised that electricity is a limited resource and in some places demand is exceeding supply or is forecast to in the near future.
It has become important to identify potential areas for saving in electricity consumption. If any savings can be made in air conditioning systems, then there is potential to make an overall huge saving in the consumption of electricity.
The saving of electricity can also lead to savings in power distribution infrastructure upgrades. Such upgrades are becoming necessary to deal with increasing peak loads introduced by a rapidly growing air conditioning market.